Fundamentals of Wearable Computers and Augmented Reality, 2nd Edition

161Visual Tracking for Augmented Reality in Natural Environments

In order to limit this computational cost in any frame, we adopt the incremental key-

point matching approach described in Section 7.2.3. Incremental keypoint matching

only attempts to match a limited number of keypoints in each frame. The selected

set varies each frame so the set of successful matches gradually accumulates. While

a few matches per frame are seldom sufcient to estimate a robust pose, successful

matches are tracked from frame to frame. By selecting new keypoints for matching

and tracking existing matches, the number of tracked matches accumulates. In our

experiments, about 10 frames are sufcient for accumulating enough matches to

recover a robust camera pose. ...